[SECURITY] Ensure decoded entities are encoded for HTML again

HTML entities being used in link tags created with `typolink` have
to be encoded correctly again after entities have been decoded for
internal processing.

Resolves: #91161
Releases: master, 9.5
Change-Id: Ifc4d2da669aab01f2b3041bb32c0a24a727634b4
Security-Bulletin: TYPO3-CORE-SA-2020-003
Security-References: CVE-2020-11065
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/64467


Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Oliver Hader <oliver.hader@typo3.org>